[mythtv] [experimental patch] vbi decoder for IVTV cards

Martin Barnasconi mythtv at barnasconi.net
Thu Mar 3 20:40:11 UTC 2005

> Using Hauppauge PVR-350 for recording, playback using EPIA TV-out
> (Unichrome & Software).
I use a PVR250 card and DVI video output (using standard Xv videooutput I 
Perhaps you are able to use the PVR350 teletext decoder and overlay of the 
card itself. Guess output is done via videoout_ivtv but no idea if the 
embedded vbi is properly passed-through to the hardware-decoder. Can someone 
> 1) 888 subtitles are not 100%, this could be reception issues -
> difficult to tell, however my picture is crystal clear and other txt
> pages I tried did not present any typical bad reception type errors.

Tetetext and subtitles (page 888) use the same routine. What do you mean with 
not 100%? Wrong characters? I disabled character conversion for the moment. 
Uncomment these and test. Other reason could be the font itself, perhaps 
special characters are not in the TTF file.

> 2) Text fonts/colours (obviously only grey scale when using
> Unichrome), I presume just a matter of tweeking the theme? But when
> using software decoding impossible to read without contrasting
> background.
TT and subtitles are all in colors. Grey stuff probably caused by unichrome TV 
out in combination with XvMC driver. I've seen some issues related to color 
and OSD for XvMC output lately in the -dev list.

> 3) OSD offsets do not work for me, so text is often off the right of the
> screen.
Offset? only TT or also other OSD overlays (like browser-info)?
> 4) Using XvMC_VLD Unichrome decoding, has the usual performance issues
> with heavy use of OSD - but then this has nothing to do with your
> patch.
Guess not.

> Can this be implimented for dvb to? I't would be great if someone make
> this work, many channels of my provider sends teletext subs.

Yes, original code was developed for DVB (thanks to Kenneth). See 

>  Either add those source files to the overall list
> of sources for libmythtv.pro, or make their usage in NVP
> conditional (#ifdef USING_IVTV).

Good point. will add sources to libmythtv.pro without any condition.
There is hardly any additional IVTV code needed to do so (I will check the 

Thanks for testing guys.


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